Apparatus and Methods for Weighted Bus Arbitration Among a Plurality of Master Devices Based on Transfer Direction And/Or Consumed Bandwidth

1. A method of performing bus arbitration among a plurality of master devices, comprising: allocating a proportionate share of bus bandwidth to each master device; tracking each master device's consumption of bus bandwidth by decrementing its allocated share in response to the length of bus transactions performed by the master device; and using each master device's remaining bandwidth share as a priority in arbitration for the bus.

2. The method of claim 1 wherein the bus comprises separate transmit and receive channels, and wherein a proportionate share of the bandwidth of each channel is separately allocated to each master, decremented in response to the length of bus transactions performed on each channel, and used in arbitration for bus transactions on each channel.

3. The method of claim 2 wherein write operations occur on the transmit channel and read operations occur on the receive channel.

4. The method of claim 2 wherein the bus further comprises a separate address channel.

5. The method of claim 2 wherein address information and write data are transmitted on the transmit channel.

6. The method of claim 1 wherein the length of a bus transaction performed by the master device is measured by a quantity of data transferred in the bus transaction.

7. The method of claim 1 wherein the length of a bus transaction performed by the master device is measured by a number of information transfer cycles required on the bus to perform the bus transaction.

8. The method of claim 7 wherein the length of a bus transaction performed by the master device is measured by a number of data transfer cycles required on the bus to perform the bus transaction.

9. The method of claim 1 further comprising reallocating a proportionate share of bus bandwidth to each master device.

10. The method of claim 9 wherein the reallocation occurs at the expiration of an arbitration interval.

11. The method of claim 10 wherein the arbitration interval is the sum of allocated shares of all master devices, in bus data transfer cycles.

12. The method of claim 10 wherein the reallocation to at least one master device occurs at a higher frequency than the reallocation to at least one other master device.

13. The method of claim 9 wherein the reallocation occurs when all master devices have fully decremented their allocated share of bus bandwidth.

14. The method of claim 1 wherein arbitration is performed on a round-robin basis when all master device's remaining bandwidth share is equal.

15. A method of performing arbitration among a plurality of master devices on a bus having separate transmit and receive channels, comprising: independently assigning an arbitration priority for the transmit and receive channels to each master device; and independently decrementing each master device's transmit and receive channel priority in response to a bus transaction performed by each respective master device on each respective channel.

16. The method of claim 15 wherein the arbitration priority assigned to each master device for each channel is a relative proportionate share of a channel's bandwidth.

17. The method of claim 16 wherein each channel priority for each master device is decremented in response to an amount of channel bandwidth consumed by each master device.

18. The method of claim 17 wherein the consumed bandwidth is measured in an amount of data transferred on a channel in the bus transaction.

19. The method of claim 17 wherein the consumed bandwidth is measured in information transfer cycles on a channel required to perform the bus transaction.

20. The method of claim 19 wherein the consumed bandwidth is measured in data transfer cycles on a channel required to perform the bus transaction.

21. The method of claim 15 further comprising reassigning an arbitration priority for the transmit and receive channels to each master device.

22. The method of claim 21 wherein the arbitration priority for each channel is reassigned at the expiration of an arbitration interval.

23. The method of claim 22 where the arbitration priority for at least one channel is reassigned to at least one master device at a higher frequency than the channel priority is reassigned to at least one different master device.

24. The method of claim 21 wherein the arbitration priority is reassigned to each master device when the priorities for the transmit or receive channel in all master devices are fully decremented.

25. The method of claim 15 wherein the bus comprises a transmit channel transferring write data and write enables, a receive channel transferring read data, and an address channel transferring address and transfer qualifier information.

26. The method of claim 25 wherein the bus comprises a transmit channel transferring write data, write enables, addresses, and transfer qualifier information, and a receive channel transferring read data.

27. The method of claim 15 further comprising arbitrating among master devices requesting the transmit or receive channels using a round-robin arbitration algorithm when the respective channel priorities for all the requesting master devices are the same.

28. A method of performing arbitration among a plurality of master devices on a bus having separate transmit and receive channels, each master device associated with a weighting register corresponding to each channel, comprising: loading the transmit channel weighting register and receive channel weighting register associated with each master device with a relative proportionate share of bandwidth on the respective channel; arbitrating among master devices requesting bus transactions on the bus channels based on current bandwidth share as reflected by the contents of the weighting registers; when a master device is granted access to a bus channel, decrementing the weighting register corresponding to that channel associated with the granted master device, by the bus channel bandwidth consumed in the granted bus transaction.

29. The method of claim 28 , wherein arbitrating among requesting master devices comprises, if all weighting registers corresponding to the requested bus channel are equal, employing a round-robin arbitration algorithm.

30. The method of claim 28 , further comprising periodically reloading the weighting registers with a relative proportionate share of bandwidth on the respective channel.

31. The method of claim 30 wherein the weighting registers are reloaded at the expiration of an arbitration interval.

32. The method of claim 30 wherein the weighting registers are reloaded when all weighting registers for a bus channel are fully decremented.

33. An electronic device, comprising: a data transfer bus; at least two master devices connected to the bus in data transfer relationship; at least one slave device connected to the bus in data transfer relationship; an arbitration priority register associated with each master device, the arbitration priority register operative to be loaded with an initial value and operative to decrement, in response to the master device being granted a bus transaction on the bus, by an amount reflecting the bus bandwidth consumed by the bus transaction; and a bus arbiter operative to grant the bus to the requesting master device with the highest value in its associated arbitration priority register.

34. The device of claim 33 , wherein the bus arbiter is further operative to grant the bus to a requesting master device on a round-robin basis when the values in arbitration priority registers associated with all requesting master devices are equal.

35. The device of claim 33 , wherein the data transfer bus comprises a transmit channel operative to transfer write data and a receive channel operative to transfer read data, and further comprising a separate arbitration priority register for each channel associated with each master device, each register operative to decrement by an amount reflecting the channel bandwidth consumed by a bus transaction, and wherein the arbiter arbitrates for each channel.

36. The device of claim 35 , wherein the transmit channel is further operative to transfer addresses.

37. The device of claim 33 wherein the arbitration priority register is further operative to be reloaded.

38. The device of claim 37 wherein the arbitration priority register is operative to be reloaded at the expiration of an arbitration interval.

39. The device of claim 37 wherein the arbitration priority register is operative to be reloaded when all of the arbitration priority registers for the transmit or receive channels are fully decremented.

40. An electronic device, comprising: at least two master devices; at least one slave device; a transmit bus channel operative to transfer information from a master device to a slave device; a receive bus channel operative to transfer information from a slave device to a master device; an arbitration priority register for each of the transmit and receive bus channels associated with each master device, the arbitration priority register operative to be loaded with an initial value and operative to decrement in response to the master device being granted a bus transaction on the respective bus channel; and a bus arbiter operative to grant a bus channel to the requesting master device with the highest value in its associated arbitration priority register for that channel.

41. The device of claim 40 , wherein the arbitration priority register for each channel is operative to decrement by an amount reflecting the associated master device's consumption of bandwidth on that channel in a granted bus transaction.

42. The device of claim 40 wherein the information transmitted from a master device to a slave device on the transmit channel includes addresses.